76 s. GOTO. 



describes a circle which is incomplete only at the hinder part. A 

 second nerve is given off towards the hinder part of the sucker ; 

 this gives off at a short distance from its origin a small branch, and 

 after this, it takes a somewhat similar course in the hinder part to 

 that pursued by the first nerve in the anterior, but remains through- 

 out separate from its fellow of the opposite side. A third nerve is 

 given oft' towards the lateral part of the sucker ; but this soon 

 proceeds forwards, and runs almost concentrically with the first 

 nerve, but outside it near the margin of the sucker. This nerve 

 could be followed only for a comparatively short distance. These 

 three nerves all take their origin at the sp.me pc^int, and are repre- 

 sented in fig. 1, n. XX. 



In Vidiilophora (PI. X, fig. 5) and Monocolijlc (V\. XVII, fig. 1), 

 the external lateral nerve could be traced along the ventrolateral border 

 of the body almost up to the point of union with the internal lateral 

 nerve ; but in all the other genera that have come under my observa- 

 tion I could follow it only for a comparatively short distance ; and 

 in these it became gradually so S]nall and its tissue so imperfectly dif- 

 fentiated from the surroundini»' mesenchvma that I could not be sure 

 whether I had the secti(3n of the nerve before me or not. The internal 

 lateral nerves, on the contrary, could always be distinctly fallowed up 

 to the region of the suckers ; and in Onchocoltße, they become con- 

 tinuous with each other and îoun a loop at about the level of the 

 second pair of suckers, on the ventral side of the intestine (PI. XV, 

 fig. 2). 



In Trisioinuni, a pair of dorsal nerves has been described by some 

 Avriters, and I have m3\self observed it in Onchocolijle ; but in all the 

 other genera, I could not demonstrate it with any satisfaction to 

 myself. 



The four posterior nerves are united with each other at regular 



